How to combine multiple OTBI Analysis into one OTBI Analysis to generate graphs?

Summary:

We have requirement to create a Turnover dashboard based on the count of unique person numbers at a point in time using OTBI analysis. As the fact columns in workforce trend subject area gives information on headcount based on FTE from positions page. And the setup for my organization is not suited for this.

I have created three analysis as per this requirement (attached below).

One to give period start headcount and second to period end headcount using presentation variable and then using the persentation variable to set prefix in advance tab to ( SET VARIABLE PARAM_EFFECTIVE_DATE='@{PV_START_DATE}{@{system.currentTime}[yyyy]-01-01}'; )